Taking vitamin supplements is thought to help ward off health problems like cancer, but a new study shows they may actually worsen conditions in some people.
Swedish researchers gave antioxidants to laboratory mice with early-stage lung cancer. Rather than staving off the cancerous growths in mice, the supplements caused the tumors to multiply and become so aggressive that the animals died twice as fast as the mice that did not receive the supplements. The researchers theorized that the extra vitamins actually blocked one of the body’s key cancer-fighting mechanisms.
General health recommendations cannot be based on animal studies, researchers pointed out, however the results should give one pause. Those at high risk for lung cancer, such as former smokers, should be aware that taking extra antioxidant supplements could speed up tumor growth.
Antioxidants are substances that may prevent or delay some types of cell damage. They are found in many foods, including fruits and vegetables. Synthetic forms are also found in dietary supplements, such as beta-carotene, lutein, lycopene, selenium, and vitamins A, C, and E.
Studies have shown mixed results when it comes to the benefit of supplements in preventing cancer, and some have shown that the vitamins can do more harm than good. For example, beta-carotene has been linked to an increased risk of lung cancer in smokers, and vitamin E supplements have been shown to increase a man’s risk of prostate cancer.
The National Cancer Institute advises patients with cancer to use antioxidants supplements with caution until more about the vitamins is known.